In recent years, an electrophotographic image forming apparatus forms an image by exposing a photosensitive member to light with a plurality of rays of laser light to meet the demand of an increase in speed of image formation.
The electrophotographic image forming apparatus supplies bias current to each of a plurality of light-emitting points of the light source to ensure emission response of laser light (light beam) with which the photosensitive member is exposed to light. Since the plurality of light-emitting points each have a unique emission characteristic (relationship between current and light power), the value of bias current is set for each of the plurality of light-emitting points. Since the emission characteristic of each light-emitting point varies depending on the temperature of the light source, the image forming apparatus executes light power control on each light-emitting point during a period in which laser light does not scan on the photosensitive member when the image forming apparatus executes image formation on a recording medium.
PTL 1 discloses an image forming apparatus that executes first light power control (APC-H in PTL 1) and second light power control (APC-L in PTL 1) on each of a plurality of light-emitting points, and hence controls the value of bias current, which is supplied to each of the plurality of light-emitting points, based on the result of the first light power control and the result of the second light power control. The image forming apparatus described in PTL 1 controls the value of current, which is supplied to each light-emitting point, in the first light power control so that the light power of laser light, which is emitted from each light-emitting point, becomes a first light power, and controls the value of current, which is supplied to each light-emitting point, in the second light power control immediately after the first light power control so that the light power of laser light, which is emitted from each light-emitting point, becomes a second light power. The image forming apparatus of PTL 1 continuously executes the first light power control and the second light power control on a single light-emitting point, and then executes the first light power control and the second light power control similarly on another light-emitting point. Thus, the image forming apparatus of PTL 1 executes the first light power control and the second light power control on all light-emitting points.